This invention relates to the field of passive integrated transponder tag interrogation systems, and specifically to an apparatus and method for remotely testing such systems.
The use of Passive Integrated Transponder (PIT) tags which may be embedded in or attached to items to be tracked and accounted for has been widespread for some time. These commonly known PIT tag systems generally comprise one or, more antenna coils so positioned as to generate a field of radiated electromagnetic energy within which the tagged item or object must pass. As generally deployed, such systems are used to track and/or count animals within which a PIT tag has been subcutaneously embedded or externally affixed. As the PIT tag traverses the radiated field of electromagnetic energy, it is energized in a manner known in the art. The PIT tag uses this energyxe2x80x94which is typically stored in a capacitive elementxe2x80x94to power a transmission circuit which emits a unique PIT tag identification signal that is detected by the aforementioned antenna element. The identification signal detected by the antenna element is then transmitted to remote processing equipment which decodes the detected signal and uses this decoded information for the purposes of counting, tracking or otherwise maintaining records pertinent to.,the population of items or animals being tracked by said system.
These commonly known and used PIT tag interrogation systems suffer from a drawback heretofore unremedied in the art, that being the ability to remotely insure proper operation of the interrogation system. This shortcoming is particularly troublesome in applications where the antenna system is located in a remote location from the control point, or in locations which are physically difficult to access, such as, for example, underwater tunnels through which PIT-tagged fish travel for identification and tracking. The present solution for testing such systems is to have a user travel to the antenna location and physically pass a PIT tag through the antenna""s radiated energy field so as to generate a tag signal detectable by the control unit. Successful receipt of the manually passed tag signal confirms that the system is operating properly. This present method of testing is expensive, resource intensive, and time consuming. Further, the difficulty in performing such an operation in fish tunnels placed underwater is obvious.
It would therefore be greatly advantageous for an apparatus or method to be developed which would alleviate the above identified shortcomings of the prior art. The present invention provides a solution.
The remotely testable PIT tag interrogation system of the present invention generally comprises a receiver/transmitter antenna, an antenna interface unit, a control unit, and a general purpose digital computer, along with associated control cabling, input keyboards, and visual displays. As used herein the terms Passive Integrated Transponder tags and/or PIT tags are used synonymously and are intended to mean any type of passive transponder which emits a signal in response to exposure to a radiated electromagnetic, electrical or magnetic energy field, such as, for example, 134 kilohertz (kHz) Transponder tags conforming to the ISO/DIS 11785 standard, or their art recognized equivalent. Such tags are commonly subcutaneously embedded in animals for the purpose of tracking and identifying them in such locations as zoos and farms, or in the wild. Such tags are also used for tagging fish and birds, as well as domestic pets. As is known in the art, and as will become evident from a further reading of the material below, systems such as the one described herein, may be deployed in numerous applications and situations limited only by the imagination of the person of skill in the art. The system of the present invention may therefore be used in any application wherein transponders are placed on objects for tracking such objects as they pass within or through the field of a bi-directional antenna which energizes the transponder and receives identifying signals therefrom. As used herein, the terms object and item are used interchangeably and mean any PIT tagged entity, animate or inanimate.
The present invention utilizes a bi-directional antenna which is deployed in a location such that animals or objects equipped with PIT tags will pass through the energy field radiated by the antenna. When passing within the energizing field, the PIT tag is energized by the electromagnetic energy radiated by the antenna. This energization is achieved by charging a storage device in the PIT tag, typically a capacitive element, which then becomes a power source the PIT tag. The PIT tag utilizes this stored energy to generate a unique tag identification signal which is received by the antenna The antenna is connected via antenna leads, in a manner commonly known in the art, to an antenna interface unit which demodulates the tag identification signal and converts it into a data signal which is passed to a control unit which logs and tracks the identification signals received. The control unit generally comprises a display and keyboard through which a user may operate the system and view information about the tags being interrogated by the system.
The control unit is typically further connected to a general purpose digital computer which can be used to remotely control the system as well as to collect and process data related to the tags interrogated and identified by the system. Additionally, the control unit, the computer, or both may be used to activate programmable logic control (PLC) devices for triggering other events, such as, for example, gate closures, alarm indications, etc.
Generally, PIT tag systems are designed to operate automatically, with little to no operator intervention. Without direct visual observation, it is therefore impossible to determine if the absence of a tag interrogation and identification cycle is due to an absence of animals or objects passing within the antenna""s radiated energy field or due to a system malfunction which is preventing tag interrogation signals from reaching the control unit. To overcome this problem, a remotely controllable PIT tag is mounted at the antenna site within the radiant energy field of the antenna. This remote test PIT tag, under the control of the system control unit and/or the attached general purpose computer, can be selectively operated so that at predetermined times the system may activate the test tag and thereby insure that the system is operating normally.
The remotely deployed test tag contains a unique identification code which when received by the system is recognized as the test tag identification code. This test tag is typically remotely activated by a relay, powered from the control unit, but deployed within the remote test tag for selectively activating and deactivating the test tag electronics. Further, varying the position of the test tag within the radiated energy field of the antenna provides an indication of the field strength of the antenna, since, if the remote test tag is fixably located at the fringes of the radiated energy field, and a remote test tag identification signal is successfully received by the control unit, this would indicate that the antenna is operating at peak performance.
In addition to the remotely controllable test tag, the system may be supplied with an additional remote test feature which, in the event of a test tag failure, will further isolate the source of the difficulty within the system. Specifically, the antenna interface unit is equipped with circuitry which permits the remote detection of the field produced by the antenna. Such a capability permits the detection of an open antenna coil or a circuitry failure in the antenna drive unit.
When operating properly, the antenna interface unit receives a signal from a PIT tag in the antenna field and digitizes it for further transmission to the control unit. The antenna may be located at a variety of distances from the antenna interface unit through antenna cabling commonly known in the art. Further, the antenna interface unit may be either remotely located or co-located with the control unit. The control unit may similarly be located near to, or remote from the general purpose computer, as application requirements dictate. Data transmission within the system may be accomplished over twisted pair cable, fiber optic cable or a combination thereof as a matter of design choice. Of course, the person of skill will recognize that the various data communication methodologies that are employed in the system may be varied to fit the application requirements to which the system is addressed, and these methodologies may be wired or wireless, metallic or optical, or any art recognized combination thereof, as a matter of design choice.